An optical communications system utilizes an optical carrier wave to transmit communications signals among various items of optical equipment that are coupled to the system and that use the system to communicate with one another. The system utilizes optical fiber cables for transmitting the carrier wave from one item of optical equipment to another. For example, an optical communications system may comprise a computer central processor unit, CPU, as one item of equipment, and a peripheral, such as a printer, as another item, and optical fiber cables linked between the CPU and Printer.
Each item of optical equipment is coupled to the system by way of an optical connector that is constructed for disconnect coupling with the optical fiber cables. A bidirectional system utilizes two optical cables, one for receiving optical signals from an item of optical equipment, and another for sending optical signals to the same item. Each item of optical equipment has an optical emitter for sending signals and optical detector for receiving signals. The optical connector for the item provides a disconnect coupling for both the optical emitter and the optical detector.
There is a need to test each item of optical equipment before installation into the communications system. Typically, this is done by simulation testing, whereby the emitter and detector of the item of optical equipment to be tested is connected to a simulator that simulates the optical system, and the operation of the item is tested as though the item were coupled into the system itself and not just the simulator.
The development of a simulator began with a device that was capable of generating special test signals or that was capable of indicating precise measurements. All of the testing was performed externally on the item of equipment being tested. As each item of optical equipment became increasingly complex, the need for testing became ever greater. In order to make the testing less expensive, there has evolved a trend toward using the internal capabilities of the equipment being tested to execute testing on itself. This evolution was feasible since the item being tested has become and continues to become improved with the addition of internal electronics that can be commanded to function, in conjunction with the simulator, to execute tests internally of the item itself. The result has been to eliminate expensive specialized testing equipment and associated testing procedures. The simulator for testing has been reduced from a device that produces complex signals or measurements, to a simplified loop back attenuator, which is defined as a communications signal path that forms a loop from the emitter to a detector of the same item of optical equipment, such that optical signals transmitted from the item under test is looped back to the same item and internally transmitted among its internal component parts. The loop back simulator purposely simulates a loss of signal intensity expected of a communications system in which the item would be installed subsequent to passing the testing procedure.
A known loop back simulator involves an optical fiber cable formed in a loop and having ends of the fiber connected with alignment ferrules. The loop is installed in an alignment fixture that will align the ends of the loop with the emitter and detector of the item to be tested. The alignment ferrules and the process of their assembly with an optical fiber is disclosed more completely in U.S. Pat. No. 3,999,837. This known simulator is costly due to the process of assembly and of polishing of the ends of the fiber as specified in the patent. The need for further reduction in cost is fulfilled by the invention.